The effect of variation of the coke microstructure with the addition of iron ore on the tensile strength of ferrous coke was investigated. To make ferrous coke, pressed mixture of Donaldson slightly coking coal, Copabella semi-anthracite coal and MBR iron ore were used. The tensile strength and elastic modulus of the ferrous coke were measured by diametral-compression test. Moreover, the homogenized elastic modulus was estimated by homogenization method using the cross sectional digital images of the ferrous coke. Both of the experimental and analytical results were compared, and the image analyses for the digital images were used to quantify the micro-properties and to investigate their effect on the tensile strength. The results were concluded as follows: (1) The tensile strength of the ferrous coke decreases with the addition of MBR iron ore when maximum fluidity of the raw materials is under 22 ddpm and swelling behavior does not develop, and the adhesion between coal particles is weak. (2) The tensile strength of the ferrous coke increases by variation of coke microstructure with the addition of MBR iron ore when maximum fluidity of the raw materials is greater than 22 ddpm and swelling behavior develops. It seems that the number of coarse-pores which behaves fracture origin decreases and the number of fine-pores which has minor influence on degradation of stiffness of the ferrous coke increases by the addition of MBR iron ore.
